Your poem has so many beautiful images. Here is my attempt to correct it. Remember that capitalization and line breaks are very important, especially in a poem! ---
He has sunflowers in his pupils. I love those flowers so I decide to be a sun.
His blond hair, like a petal of the flower, is very soft and warm, whereas I have a hot sun in my pupils. My black hair, like the sunshine, is very strong and thick.
In the night, when the frog is crying, the flower sleeps. The sun has waited for the frog to become a prince.
In the morning the sunflower envies the frog and turns its back to the sun. The sun trys to soothe the sunflower with its shining.
Unnoticed the sunflower turns its face to the sun. The flower's sweet smell fills all the air.
